Information processing apparatus and information processing method

ABSTRACT

A tomogram of an object is acquired. A place in a tomogram which corresponds to a portion spaced apart from a reference point in the object by a predetermined distance is specified. A composite image is generated by combining the tomogram with information indicating the specified place. The composite image is output.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique of handling tomograms.

2. Description of the Related Art

In the medical field, a doctor makes a diagnosis by using the medicalimages (three-dimensional image data representing three-dimensionalinformation inside an object) captured by a plurality of modalities ormedical images captured on different dates. In order to use a pluralityof types of medical images for a diagnosis, it is important to associate(identify) a region (a region or lesion of interest) such as a lesion ofinterest on each medical image. For this reason, the doctor searches fora region (a corresponding region or lesion) corresponding to a lesion ofinterest pointed out on one medical image from another medical image byusing, as clues, similarities in terms of the shape of the lesion, theappearance of a neighboring portion of the lesion, and the like, whileseeing the image of the lesion of interest.

In a breast oncology department, after a lesion or the like on an MRIimage of the breast imaged in a prone posture is pointed out, a doctorsometimes makes a diagnosis upon searching for (identifying) acorresponding lesion on an ultrasonic tomogram by an ultrasonicexamination in a supine posture. However, since the breast as an objectis soft and large differences appear between body postures, the positionand appearance of a lesion greatly change. This makes it difficult tosearch for a corresponding lesion. Demands have therefore arisen for areduction in load by some kind of computer aid.

Patent literature 1 (Japanese Patent Laid-Open No. 2011-123682)discloses a technique of estimating the deformation of the breast from aprone posture to a supine posture. Using this deformation estimationresult can estimate the position of a lesion in a supine posture andpresent the estimated position as support information for the operationof an ultrasonic probe. In addition, patent literature 2 (JapanesePatent Laid-Open No. 2010-227215) discloses a technique of automaticallyextracting a nipple position from a simple X-ray image of the breast anddrawing a region in an image which is included in a predetermined rangefrom the nipple position in the image.

When using the method disclosed in patent literature 1, since it isnecessary to perform calculation for a deformation simulation such as afinite element method, the operator (doctor) needs to wait until the endof the calculation. In addition, there are several types of measurementinformation which the operator should input for the execution of adeformation simulation, but the operator is sometimes not allowed totake time and effort to input such information. In addition, it is noteasy to accurately estimate the deformation of the breast itself. Inaddition, the method disclosed in patent literature 2 allows theoperator to know a region within a predetermined range from a featurepoint of an object. This region is limited to only a slice including thefeature point in the image. It is therefore impossible to know theregion on an arbitrary slice.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the aboveproblems, and provides a technique for deriving support informationbeing used when searching for a lesion or the like in an image by onlysimple calculation, without using many pieces of measurementinformation, and presenting the support information.

According to the first aspect of the present invention, there isprovided an information processing apparatus comprising: a unitconfigured to acquire a tomogram of an object; and a generation unitconfigured to specify a place in the tomogram which corresponds to aportion spaced apart from a reference point in the object by apredetermined distance, generate a composite image by combining thetomogram with information indicating the specified place, and output thecomposite image.

According to the second aspect of the present invention, there isprovided an information processing apparatus comprising: a unitconfigured to acquire a tomogram of an object; a unit configured toacquire a predetermined distance as a distance from a reference point inthe object to a lesion in the object; a unit configured to specify aplace in the tomogram which corresponds to a portion spaced apart from aposition of the reference point by the predetermined distance; and aunit configured to combine information indicating the place with thetomogram and output a composite result.

According to the third aspect of the present invention, there isprovided an information processing method performed by an informationprocessing apparatus, comprising: a step of acquiring a tomogram of anobject; and a generation step of specifying a place in the tomogramwhich corresponds to a portion spaced apart from a reference point inthe object by a predetermined distance, generating a composite image bycombining the tomogram with information indicating the specified place,and outputting the composite image.

According to the fourth aspect of the present invention, there isprovided an information processing method performed by an informationprocessing apparatus, comprising: a step of acquiring a tomogram of anobject; a step of acquiring a predetermined distance as a distance froma reference point in the object to a lesion in the object; a step ofspecifying a place in the tomogram which corresponds to a portion spacedapart from a position of the reference point by the predetermineddistance; and a step of combining information indicating the place withthe tomogram and outputting a composite result.

According to the fifth aspect of the present invention, there isprovided an information processing apparatus comprising: a tomogramacquisition unit configured to acquire a tomogram of an object; areference point position acquisition unit configured to acquire athree-dimensional position of a reference point in the object; aposition and orientation acquisition unit configured to acquire aposition and orientation of the tomogram; and a display unit configuredto superimpose and display, on the tomogram, information concerning athree-dimensional distance from the reference point to each point on thetomogram based on the three-dimensional position of the reference pointand the position and orientation of the tomogram.

According to the arrangement of the present invention, it is possible toderive support information when searching for a lesion or the like in animage by only simple calculation, without using many pieces ofmeasurement information, and present the support information.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of the functionalconfiguration of an information processing system;

FIG. 2 is a block diagram showing an example of the hardwareconfiguration of a computer;

FIG. 3 is a flowchart showing the processing performed by the computer;

FIG. 4 is a view showing an example of a composite image;

FIG. 5 is a block diagram showing an example of the functionalconfiguration of the information processing system;

FIG. 6 is a flowchart showing the processing performed by the computer;

FIG. 7 is a view showing an example of a composite image;

FIG. 8 is a view showing an example of a composite image;

FIG. 9 is a view showing an example of a composite image;

FIG. 10 is a view showing an example of a composite image;

FIGS. 11A and 11B are views for explaining information held in a dataserver 560;

FIGS. 12A and 12B are views for explaining statistic information;

FIG. 13 is a block diagram showing an example of the functionalconfiguration of an information processing system;

FIG. 14 is a flowchart showing the processing performed by a computer;and

FIG. 15 is a view for explaining an example of a composite imageaccording to the third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described with reference tothe accompanying drawings. Note that each embodiment to be describedbelow will exemplify a case in which the present invention isspecifically carried out, and is a specific embodiment having anarrangement described in the scope of claims.

First Embodiment

An information processing system according to this embodiment presentssupport information for a search to an operator when searching(identifying) for a corresponding region on an ultrasonic tomogram andperforming diagnosis by an ultrasonic examination upon pointing out aregion of interest such as a lesion on the image acquired by a modalitysuch as MRI. This system presents a place where the possibility of thepresence of a corresponding region is high on an ultrasonic tomogram,based on findings that the three-dimensional distance from the nipple toa region of interest such as a lesion (the distance between the nippleand the region of interest) tends to be kept constant, when the breastis an examination target, regardless of a difference in body posturebetween, for example, a prone posture and a supine posture. In addition,information which allows the operator to grasp the distance from thenipple to each point on an image is displayed on an ultrasonic tomogramto facilitate a search for a corresponding region on the ultrasonictomogram. The information processing system according to this embodimentwill be described below.

An example of the functional configuration of the information processingsystem according to this embodiment will be described first withreference to the block diagram of FIG. 1. As shown in FIG. 1, theinformation processing system according to the embodiment includes adata server 160, an information processing apparatus 100, a medicalimage collection apparatus 170, and a display unit 180.

The data server 160 will be described first. The data server 160 holdsinformation such as a three-dimensional distance from a reference point(the nipple) on an object as an observation target to a region ofinterest (the distance between the reference point and the region ofinterest), and outputs the information to the information processingapparatus 100. The distance between the reference point and the regionof interest which is held by the data server 160 is a numerical valuecalculated in advance from other three-dimensional medical images suchas MRI images captured by imaging the same object. This value can beacquired by, for example, making the image processing system (not shown)detect the position of the reference point (nipple position) from an MRIimage by image processing and calculate the three-dimensional distancebetween the detected position and the position of a region of interestpointed out on the same image by the operator.

Although FIG. 1 shows the data server 160 as an external apparatus ofthe information processing apparatus 100, the server may be a deviceincorporated in the information processing apparatus 100 and may be, forexample, a device such as a hard disk incorporated in the informationprocessing apparatus 100.

The medical image collection apparatus 170 will be described next. Inthis embodiment, the medical image collection apparatus 170 will bedescribed as an ultrasonic image diagnosis apparatus. The medical imagecollection apparatus 170 captures an ultrasonic tomogram (tomogram) ofan object in real time. The medical image collection apparatus 170sequentially inputs the ultrasonic tomograms of the respective framescaptured by the medical image collection apparatus 170 to theinformation processing apparatus 100 via a tomogram acquisition unit110. The medical image collection apparatus 170 also includes a sensorsystem for measuring the position and orientation (three-dimensionalposition and orientation) of an ultrasonic prove (not shown) in a spacein real time. The positions and orientations of the ultrasonic probewhich are measured by this sensor system are sequentially input to theinformation processing apparatus 100 via the position and orientationacquisition unit 120. The sensor system for measuring the position andorientation of the ultrasonic probe may have various arrangements. Forexample, the sensor system may capture an image of the ultrasonic probein real time and calculate the position and orientation of theultrasonic probe from the image by calculation or may measure theposition and orientation by a known measurement method using a magneticsensor, ultrasonic sensor, or optical sensor. The information processingapparatus 100 will be described next. As the information processingapparatus 100, for example, a general PC (Personal Computer) ordedicated hardware can be used.

A reference distance acquisition unit 105 acquires the distance betweena reference point and a region of interest sent from the data server 160as a reference distance. As described above, the tomogram acquisitionunit 110 transfers the ultrasonic tomograms sequentially sent from themedical image collection apparatus 170 to an image generation unit 140on the subsequent stage. As described above, a position and orientationacquisition unit 120 transfers the positions and orientationssequentially sent from the medical image collection apparatus 170 to theimage generation unit 140 on the subsequent stage.

A reference point position acquisition unit 130 acquires the position ofa reference point in a space by using the position and orientation ofthe ultrasonic probe based on an instruction from the operator.

Based on the reference distance, the position of the reference point,and the position and orientation of the ultrasonic prove, the imagegeneration unit 140 calculates a portion (circle) obtained by cutting asphere centered on the reference point and having the reference distanceas a radius along a slice corresponding to an ultrasonic tomogram byperforming calculation processing (to be described later). The imagegeneration unit 140 then superimposes (combines) information concerninga portion (arc) of the calculated circle, which is included in theultrasonic tomogram, on the ultrasonic tomogram, and sends the resultantimage to a display control unit 150.

The display control unit 150 sends the composite image sent from theimage generation unit 140, that is, the image obtained by superimposingthe information concerning the arc on the ultrasonic tomogram, to thedisplay unit 180 to make it display the image.

The display unit 180 is formed from a CRT, liquid crystal displayscreen, or the like, and displays the processing result obtained by theinformation processing apparatus 100 in the form of images, characters,or the like. The display unit 180 can display, for example, a compositeimage (to be described later), GUI (Graphical User Interface), and thelike.

The respective functional units constituting the information processingapparatus 100 may all be implemented by hardware but may partly beimplemented by software (computer programs). In this case, the controlunit of the information processing apparatus 100 executes such softwareto implement a corresponding function. In addition, one or more of therespective functional units constituting the information processingapparatus 100 may be implemented as independent external devices.Obviously, the respective functional units constituting the informationprocessing apparatus 100 may be implemented by software.

Assume that in this embodiment, all the functional units constitutingthe information processing apparatus 100 are implemented as software. Inthis case, a computer having a hardware configuration shown in FIG. 2can be applied to the information processing apparatus 100.

A CPU 1001 controls the overall operation of a computer by usingcomputer programs and data stored in a RAM 1002 and a ROM 1003, andexecutes each processing (to be described later) performed by theinformation processing apparatus 100 to which the computer is applied.

The RAM 1002 has an area for temporarily storing computer programs anddata loaded from an external storage apparatus 1007 and a storage mediumdrive 1008 and data received from an external device via an I/F(Interface) 1009. The RAM 1002 has a work area used when the CPU 1001executes various types of processing. That is, the RAM 1002 can providevarious types of areas, as needed. The ROM 1003 stores set data, bootprograms, and the like for this computer.

A keyboard 1004 and a mouse 1005 are used for inputting various types ofinstructions to the CPU 1001 when the operator operates this computer.Therefore, any devices other than the keyboard 1004 and the mouse 1005may be used as long as they are devices for inputting various types ofinstructions to the CPU 1001.

The external storage apparatus 1007 functions as a large-capacityinformation storage apparatus such as a hard disk drive apparatus. Theexternal storage apparatus 1007 stores an OS (Operating System) andcomputer programs and data for making the CPU 1001 execute therespective types of processing to be described later as those executedby the information processing apparatus 100 using this computer. Thecomputer programs stored in the external storage apparatus 1007 includecomputer programs for making the CPU 1001 execute the functions of thefunctional units (105 to 150) shown in FIG. 1 as functional units in theinformation processing apparatus 100. The data stored in the externalstorage apparatus 1007 include those handled as known information in thefollowing description.

The computer programs and data described as those stored in the externalstorage apparatus 1007 are loaded into the RAM 1002 and become targetsto be processed by the CPU 1001, as needed, under the control of the CPU1001. Note that the information described as that stored in the dataserver 160 may be stored in the external storage apparatus 1007.

The storage medium drive 1008 reads out a computer program and datastored in a storage medium such as a CD-ROM or DVD-ROM in accordancewith an instruction from the CPU 1001, and outputs them to the RAM 1002or the external storage apparatus 1007. Some of the computer programsand data described as those stored in the external storage apparatus1007 may be stored in this storage medium.

An I/F 1009 is constituted by a digital input/output port such as ananalog video port or IEEE1394, an Ethernet port for outputtinginformation such as a composite image to the outside, and the like. Thedata server 160, the medical image collection apparatus 170, and thedisplay unit 180 are connected to the I/F 1009. Note that in one form ofimplementation, some of the functions of the reference distanceacquisition unit 105, the tomogram acquisition unit 110, the positionand orientation acquisition unit 120, and the reference point positionacquisition unit 130 are implemented by the I/F 1009. The respectiveunits described above are connected to each other via a bus 1010.

The processing performed by the computer in FIG. 2 which operates as theinformation processing apparatus 100 will be described next withreference to FIG. 3 showing a flowchart for the processing. Note thatcomputer programs and data which cause the CPU 1001 to executeprocessing in accordance with the flowchart of FIG. 3 are stored in theexternal storage apparatus 1007. The CPU 1001 loads such computerprograms and data from the external storage apparatus 1007 into the RAM1002 and executes processing by using the computer programs and data.This causes the computer in FIG. 2 to execute processing in accordancewith the flowchart of FIG. 3.

(Step S3000: Acquisition of Reference Distance)

In step S3000, the CPU 1001 functions as the reference distanceacquisition unit 105 to acquire the distance between the reference pointand the region of interest sent from the data server 160 as a referencedistance. Assume that the data server 160 does not hold the distancebetween the reference point and the region of interest, and hence it isnot possible to obtain the distance between the reference point and theregion of interest from the data server 160. In this case, no referencedistance is acquired in this step.

(Step S3010: Acquisition of Tomogram)

In step S3010, the CPU 1001 functions as the tomogram acquisition unit110 to acquire an ultrasonic tomogram from the medical image collectionapparatus 170. In addition, in this step, the CPU 1001 functions as theposition and orientation acquisition unit 120 to acquire the positionand orientation of the ultrasonic probe from the medical imagecollection apparatus 170 when it has captured the ultrasonic tomogram.

(Step S3020: Acquisition of Reference Point Position)

In step S3020, the CPU 1001 functions as the reference point positionacquisition unit 130 to acquire the position of the reference point(nipple position) in a space. In this acquisition processing, when theoperator operates the keyboard 1004 (for example, presses a key assignedwith a reference point position acquisition command) while keeping apredetermined portion of the ultrasonic probe (for example, the centralportion of the prove surface) in contact with the nipple position of theobject. That is, when the operator executes the above operation, the CPU1001 obtains the position of the above predetermined portion from theposition and orientation of the ultrasonic probe which is acquired bythe position and orientation acquisition unit 120, and acquires theobtained position as the position of a reference point. When obtainingthe position of the above predetermined portion from the position andorientation of the ultrasonic probe, the CPU 1001 may use a method ofapplying a predetermined bias to the position and orientation or amethod of performing predetermined matrix transformation.

Note that if a reference point exists inside the body of the object, theoperator operates the ultrasonic probe to draw the reference point on anultrasonic tomogram. Thereafter, the operator points out the coordinatesof the reference point on the tomogram to acquire the position of thereference point.

(Step S3030: Image Combining)

In step S3030, the CPU 1001 functions as the image generation unit 140to generate an image by superimposing information representing a placewhere the possibility of the presence of a corresponding region is highon an ultrasonic image, and sends the resultant image to the displayunit 180.

The processing performed by the image generation unit 140 (CPU 1001)will be described here. First of all, the image generation unit 140obtains a sphere centered on the position of the reference pointobtained in step S3020 and having the reference distance obtained instep S3000 as a radius. The image generation unit 140 obtains a plane ina space containing an ultrasonic tomogram (that is, an ultrasonic slice(imaging slice)) based on the position and orientation of the ultrasonicprobe obtained in step S3010, and calculates a circle obtained bycutting the sphere along the plane. Finally, the image generation unit140 generates a composite image by superimposing a portion (arc), of thecalculated circle, which is included in the ultrasonic tomogram, on theultrasonic tomogram.

FIG. 4 shows an example of a composite image generated by thisprocessing. Referring to FIG. 4, an arc 430, of a circle obtained bycutting a sphere centered on a nipple position 410 as the position of areference point and having a reference distance 420 as a radius alongthe plane, which is included in an ultrasonic tomogram is superimposedon an ultrasonic tomogram 440. In this case, the arc 430 is a set ofpoints whose three-dimensional distances from the nipple position 410coincide with the reference distance obtained in step S3000. If thethree-dimensional distance from the nipple to the lesion of object ismaintained, since a corresponding region 450 does not exist except forthe vicinity of the arc 430, the operator can search for thecorresponding region 450 relying on the arc 430.

Note that auxiliary information indicating how much each point on anultrasonic tomogram differs from the reference distant as a reference(information indicating the relationship between the reference distanceand the three-dimensional distance from the reference point to eachpoint on the tomogram) may be presented while being superimposed on thisultrasonic tomogram. For example, several distances are obtained byadding and subtracting predetermined values to and from the referencedistance. With regard to the respective obtained distances, spheres areobtained, which are centered on the position of the reference pointobtained in step S3020 and have the respective distances as radii.Circles are then obtained in the same manner as described above bycutting the spheres obtained with respect to the respective distancesalong the above plane, and portions (arcs), of the obtained circles,which are included in the ultrasonic tomogram are superimposed on theultrasonic tomogram, thereby generating a composite image.

FIG. 7 shows an example of a composite image generated by thisprocessing when a plurality of values (for example, 5 mm, 10 mm, and 15mm) set at equal intervals are used as predetermined values. Referringto FIG. 7, the arcs obtained from several concentric spheres having, asradii, the values obtained by adding and subtracting the predeterminedvalues to and from the reference distance are superimposed as auxiliarylines 735 on the ultrasonic tomogram 440, together with the arc 430 inFIG. 4. In addition, pieces of character information (“−5 mm”, “+10 mm”,and the like) indicating how much the respective auxiliary lines differfrom the reference distance are superimposed near the auxiliary lines asadditional information. Display such a composite image on the displayunit 180 allows the operator to know how much each point on the imagediffers from the distance between the reference point and the region ofinterest. Note that the line type and color of each auxiliary line maybe changed in accordance with the difference from the referencedistance. These auxiliary lines may always be drawn or the operator mayselect to draw or not draw them by operating the keyboard 1004 or themouse 1005.

Note that if no reference distance is acquired in step S3000, the imagegeneration unit 140 executes the following processing instead of theabove processing. First of all, the image generation unit 140 calculatesa plurality of spheres centered on the position of the reference pointobtained in step S3020 and having predetermined distances (for example,distances set at intervals of 10 mm from 10 mm to 100 mm) as radii. Theimage generation unit 140 then calculates circles obtained by cuttingthese spheres along an ultrasonic slice based on the position andorientation of the ultrasonic probe obtained in step S3010. The imagegeneration unit 140 generates a composite image by superimposing, on theultrasonic tomogram, portions (arcs), of the plurality of calculatedcircles, which are included in the ultrasonic tomogram and pieces ofinformation indicating the respective distances. FIG. 8 shows an exampleof a composite image generated by this processing. Referring to FIG. 8,the arcs obtained from concentric spheres centered on the nippleposition 410 and having predetermined distances (20 mm to 60 mm) asradii are superimposed as arcs 830 on the ultrasonic tomogram 440. Thisdisplay is especially effective when the operator grasps in his/her mindthe distance between the reference point and the region of interest.That is, even if the system has not acquired the distance between thereference point and the region of interest, the operator can search forthe corresponding region 450 relying on the pieces of informationconcerning the distances from nipple presented on the ultrasonictomogram. Even if a reference distance has been acquired in step S3000,the operator may arbitrarily switch between display (display of thedistance between the reference point and the region of interest) andmain display (display of distances at predetermined equal intervals) inaccordance with an instruction issued by the operator via the keyboard1004 or the mouse 1005. Alternatively, the system may be configured topresent a mixture of these pieces of information. Note that if theposition of the reference point has not been acquired, the imagegeneration unit 140 outputs the ultrasonic tomogram.

(Step S3040: End Determination)

In step S3040, the CPU 1001 determines whether to end the overallprocessing. For example, upon detecting that the operator has pressed apredetermined key (end key) of the keyboard 1004, the CPU 1001determines that the processing is to end.

Upon determining that the processing is to end, the CPU 1001 ends theoverall processing. In contrast to this, if the CPU 1001 determines thatthe processing is not to end, the process returns to step S3010 toexecute the processing in step S3010 and the subsequent steps withrespect to a newly captured ultrasonic tomogram.

Note that this embodiment has exemplified the case in which the breastis set as an object, and the nipple is set as a reference point.However, the object and reference point to be used are not specificallylimited as long as the corresponding object exhibits a tendency that thedistance between a region of interest and a reference point ismaintained.

As described above, this embodiment allows the operator to easily graspthe three-dimensional distance from the reference point (nipple) to eachpoint on an ultrasonic image. It is possible to present the operatorwith a place where the possibility of the presence of a correspondingregion is high by, especially, indicating a point or neighboring pointwhose distance from the reference point (nipple) is “distance betweenreference point and region of interest”. According to the embodiment,since indications for a search for a corresponding region in anultrasonic tomogram are displayed in the ultrasonic tomogram, theoperator can limit a search range for the corresponding region. Inaddition, limiting a search range can reduce the operation load on theoperator and reduce the risk of wrong association. In addition, sinceany calculation such as deformation estimation is not performed, it ispossible to support a search for a corresponding region without makingthe operator wait. Furthermore, since the amount of necessary inputinformation is small, it is possible to support a search for acorresponding region without troubling the operator.

Modification of First Embodiment

The first embodiment has exemplified the case in which an ultrasonicimage diagnosis apparatus is used as the medical image collectionapparatus 170. However, the medical image collection apparatus 170 maybe any other modality. If the medical image collection apparatus 170 isCT or MRI, the information processing apparatus 100 acquires athree-dimensional image in advance. In the processing in step S3010, aslice of interest is designated by using a GUI on a known medical imageviewer, and a tomogram may be acquired from the three-dimensional image.In addition, the position and orientation of the slice may be acquired.In addition, in the processing in step S3020, the three-dimensionalcoordinates of a reference point in the three-dimensional image may beacquired by using a GUI like that incorporated in a known medical imageviewer.

In addition, the distance between the reference point and the region ofinterest held by the data server 160 need not be the one obtained froman MRI image. For example, this distance may be the one obtained byobtaining the position of a reference point and the position of a regionof interest from an image obtained by another type of modality orobtained in a past ultrasonic examination.

In addition, in the first embodiment, the reference distance acquisitionunit 105 has acquired the distance between the reference point and theregion of interest from the data server 160. However, a method ofacquiring the distance between the reference point and the region ofinterest is not limited to this. For example, the reference distanceacquisition unit 105 may acquire, as a reference distance, the distanceinput by the operator using a GUI (not shown) and the keyboard 1004 orthe mouse 1005. Furthermore, the reference distance acquisition unit 105may acquire a medical image of an object from the data server 160, andacquire the position of a region of interest and the position of areference point (nipple position) from the medical image, therebycalculating the distance between the reference point and the region ofinterest. Alternatively, the reference distance acquisition unit 105 mayacquire a medical image of an object and the position of a region ofinterest from the data server 160, and acquire only the position of areference point from the medical image, thereby calculating the distancebetween the reference point and the region of interest. Note that whenthe reference distance acquisition unit 105 is to acquire the positionof a region of interest and the position of a reference point from amedical image, the operator may manually input the positions, or thepositions may be automatically detected by image processing.

Second Embodiment

The first embodiment has exemplified the embodiment which can becommonly applied to any targets (is not limited to any specific target)exhibiting a tendency that the distance between a reference point and aregion of interest is maintained. The second embodiment will exemplify acase in which the distance between the nipple and a region of interestis acquired from an MRI image in a prone posture, and a target, that is,an organ (breast), a reference point (nipple), and preceding andsucceeding postures (prone and supine postures) are specified as whensupporting an ultrasonic examination in a supine posture. Thisembodiment has a feature of acquiring the statistic information of thedistances between reference points and regions of interest concerningsuch specific objects and controlling support information based on thestatistic information. The embodiment also has a feature of controllingsupport information based on statistic information corresponding to theattributes of an object and a region of interest in consideration of thefact that the statistic behaviors of the distances between nipples andregions of interest differ from each other depending on the attributesof objects and regions of interest. In this case, the attributes ofobjects and regions of interest are those known to make the statisticbehaviors of the distances between nipples and regions of interestdiffer from each other depending on the differences between theattributes. For example, such attributes include the ages of subjects,the breast sizes, and regions to which regions of interest belong in thebreasts. An information system according to the embodiment having as itsfeature to control display by using statistic information will bedescribed concerning only differences from the first embodiment. Thatis, the remaining portions are the same as in the first embodimentunless specifically mentioned in the following.

An example of the functional configuration of the information processingsystem according to this embodiment will be described with reference tothe block diagram of FIG. 5. Note that the same reference numerals as inFIG. 5 denote the same functional units in FIG. 1, and a description ofthem will be omitted. As shown in FIG. 5, the information processingsystem according to this embodiment includes a data server 560, aninformation processing apparatus 500, a medical image collectionapparatus 170, and a display unit 180.

The data server 560 holds, in addition to the distance between thereference point and the region of interest of an object, thethree-dimensional image data of the object, based on which the distancebetween the reference point and the region of interest is acquired. Thedata server 560 also holds the position (three-dimensional coordinates)of the region of interest in the three-dimensional image data. Inaddition, the data server 560 holds information representing a specificregion in the breast to which a region of interest belongs. For example,the data server 560 holds information representing whether the region ofinterest belongs to the inside or the outside of the breast, as shown inFIG. 11A. Alternatively, the data server 560 holds informationrepresenting whether the region of interest belongs to any of region A(inside upper portion), region B (inside lower portion), region C(outside upper portion), region D (outside lower portion), and region E(areola portion) of the breast, as shown in FIG. 11B. The data server560 also holds information representing the age and breast size (cupsize, the volume of a breast region, or the like) of a subject and thelike. The data server 560 outputs the above held data to the informationprocessing apparatus 500.

A corresponding distance calculation unit 510 acquires, from the dataserver 560, the three-dimensional image data of each subject, theposition of a region of interest in the three-dimensional image data,information representing a specific region in the breast to which theregion of interest belongs, information of the age and breast size ofeach subject, and the like. The corresponding distance calculation unit510 acquires the statistic information of the distances betweenreference points and regions of interest based on these pieces ofinformation, and calculates an estimated value of the distance betweenthe reference point and a corresponding region (to be referred to as thecorresponding distance hereinafter) from the distance between thereference point and the region of interest (reference distance) based onthis statistic information. The calculated value of the correspondingdistance is output to an image generation unit 540.

Statistic information and a corresponding distance in this embodimentwill be described below. If, for example, there is statistic informationindicating that when a body posture changes from a prone posture to asupine posture, the distance between the nipple and the region ofinterest increases by α times on the average, the value obtained bymultiplying a reference distance r [mm] by α is set as a correspondingdistance r′ (the distance at which the corresponding region most likelyto exist). Alternatively, if there is statistic information indicatingthat when a body posture changes from a prone posture to a supineposture, the distance between the nipple and the region of interest ismaintained at a standard deviation σ [mm], distances respectivelyrepresented by r−2σ, r−σ, r+σ, and r+2σ are set as correspondingdistances (information representing the range of distances at which thecorresponding region likely to exist). In addition, assume that if α andσ described above have been obtained, r′−2σ, r′−σ, r′+σ, and r′+2σ areset as corresponding distances. That is, statistic information in thisembodiment represents the above magnification α and standard deviationσ. In addition, assume that a corresponding distance represents adistance at which a corresponding region is likely to exist after achange in body posture or the range of such distances, which is derivedfrom these pieces of statistic information and reference distances.

The corresponding distance calculation unit 510 manages α and σdescribed above as pieces of statistic information independent of anobject, which are calculated by performing statistic processing for manycases (without distinguishing between the cases) by using themeasurement values of the distances between the nipples and regions ofinterest in prone postures and supine postures which have been collectedfrom the cases. The corresponding distance calculation unit 510 managesthe statistic information for each of regions (inside and outsideregions or regions A to E), which is calculated by performing statisticprocessing for many cases for each region upon classifying the casesaccording to the regions to which lesions belong. Likewise, thecorresponding distance calculation unit 510 manages statisticinformation for each segment based on each criterion, which iscalculated by performing statistic processing for many cases uponsegmenting the ages and breast sizes of subjects, the distances betweennipples and regions of interest, the distances between body surfaces andregions of interest, mammary gland densities, and the like intopredetermined segments and classifying the many cases according to therespective criteria. Note that it is not essential to use the valuesobtained by actually performing statistic processing for many cases asstatistic information, and it is possible to use the values manually set(by the apparatus designer or the like).

Note that the manner of managing statistic information is not limited tothe method of holding statistic information for each segment, which hasundergone statistic processing, and another method may be used. Forexample, a function of x approximating statistic information may beheld, with an input parameter x being a combination of at least one ormore of the age of each subject, the breast size, the distance betweenthe nipple and the region of interest, the distance between the bodysurface and the region of interest, the mammary gland density, and thelike. That is, statistic information may be managed in the form offunction f_α(x) which inputs x and outputs α or function f_α(x) whichinputs x and outputs σ.

Based on the corresponding distance calculated by the correspondingdistance calculation unit 510, the reference point position, and theposition and orientation of the ultrasonic probe, the image generationunit 540 calculates a circle obtained by cutting a sphere centered onthe reference point and having the corresponding distance as a radiusalong a slice. The image generation unit 540 generates a composite imageby superimposing, on the ultrasonic tomogram, information concerning aportion (arc), of the calculated circle, which is included in theultrasonic tomogram, and sends the image to a display control unit 150.That is, the composite image is generated in this embodiment in the samemanner as in the first embodiment except that a corresponding distanceis used instead of a reference distance.

Note that when the respective functional units in the informationprocessing apparatus 500 shown in FIG. 5 are implemented by computerprograms, the computer in FIG. 2 can be applied to the informationprocessing apparatus 500 as in the first embodiment. That is, when therespective functional units in the information processing apparatus 500are implemented by computer programs, a CPU 1001 executes the computerprograms to make the computer function as the information processingapparatus 500.

The processing performed by the computer in FIG. 2 which operates as theinformation processing apparatus 500 will be described with reference toFIG. 6 showing a flowchart for the processing. Note that an externalstorage apparatus 1007 stores computer programs and data which make theCPU 1001 execute the processing based on the flowchart of FIG. 6. TheCPU 1001 loads the computer programs and data from the external storageapparatus 1007 into a RAM 1002, and executes processing by using thecomputer programs and data. This makes the computer in FIG. 2 executethe processing based on the flowchart of FIG. 6.

Steps S6000, S6010, S6020, and S6040 in FIG. 6 are the same as stepsS3000, S3010, S3020, and S3040 in the flowchart shown in FIG. 3, andhence a description of these steps will be omitted.

(Step S6003: Acquisition of Calculation Method)

In step S6003, the CPU 1001 acquires the corresponding distancecalculation method input by the operator by, for example, pressing apredetermined key on the keyboard 1004. In this embodiment, the operatorselects one of the following calculation methods:

1. calculation based on statistic information independent of an object;2. calculation based on a region to which a region of interest belongs;3. calculation based on the age and breast size of a subject;4. calculation based on the distance from a nipple to a region ofinterest (distance between the nipple and the region of interest);5. calculation based on the distance from a body surface to a region ofinterest (distance between the body surface and the region of interest);and6. calculation based on the mammary gland density of an object.

For example, a GUI displaying these six options in a selectable manneris displayed on a display unit 180. When the operator inputs aninstruction to select one of these six options by using the keyboard1004 or a mouse 1005, the CPU 1001 may detect the selected option as acalculation method to be used subsequently.

Obviously, the method of designating a calculation method is not limitedto this method. A calculation method may be determined in advance ordetermined in accordance with examination contents or the department towhich the computer belongs. In addition, options (calculation methods)are not limited to the above six methods.

(Step S6005: Acquisition of Various Types of Data)

In step S6005, the CPU 1001 functions as a corresponding distancecalculation unit 510. This makes the CPU 1001 acquire, from the dataserver 560, a reference distance, the three-dimensional image data of anobject, the position of a region of interest in the three-dimensionalimage data, information indicating a specific region in the breast towhich the region of interest belongs, the age and breast sizeinformation of the subject, and the like.

(Step S6025: Calculation of Corresponding Distance)

In step S6025, the CPU 1001 functions as the corresponding distancecalculation unit 510 to calculate the above corresponding distance basedon the data acquired in step S6005. The CPU 1001 executes thisprocessing by obtaining the magnification α and the standard deviation σas statistic information and obtaining the representative value r′ of acorresponding distances and its range of r′−2σ, r′−σ, r′+σ, and r′+2σfrom the reference distance r based on the obtained values.

If method 1 (calculation based on statistic information independent ofan object) is selected in step S6003, the CPU 1001 selects the pieces ofstatistic information α and σ independent of an object as statisticinformation to be used subsequently.

If method 2 in step S6003 (calculation based on a region to which aregion of interest belongs), the CPU 1001 selects, as statisticinformation to be used subsequently, the values of α and σ correspondingto a region (one of inside and outside regions or one of regions A to E)to which the region of interest acquired in step S6005 belongs. Assumethat a region of interest in subject 1 exists in region C, and a regionof interest in subject 2 exists in region B, as shown in FIG. 12A. Inthis case, in processing in this step, the CPU 1001 selects amagnification αC and a variance σC which are pieces of statisticinformation corresponding to region C in the case of subject 1. In thecase of subject 2, the CPU 1001 selects a magnification αB and avariance σB which are pieces of statistic information corresponding toregion B.

If method 3 (calculation based on the age and breast size of a subject)is selected in step S6003, the CPU 1001 selects, as statisticinformation to be used subsequently, the values of α and σ correspondingto a combination of the age and breast size of the subject acquired instep S6005.

If method 4 (calculation based on the distance between the nipple andthe region of interest) is selected in step S6003, the CPU 1001 selects,as statistic information to be used subsequently, the values of α and σcorresponding to the distance between the nipple and the region ofinterest acquired in step S6000.

If method 5 (calculation based on the distance between the body surfaceand the region of interest) is selected in step S6003, the CPU 1001derives the body surface and the region of interest, and selects thevalues of α and σ corresponding to the derived distance between the bodysurface and the region of interest as statistic information to be usedsubsequently. In this case, the CPU 1001 derives the distance betweenthe body surface and the region of interest by the following processing.First of all, the CPU 1001 functions as the corresponding distancecalculation unit 510 to derive a body surface region (a boundary regionbetween the breast region and the outside of the body) by performingimage processing for three-dimensional image data. The CPU 1001 thensearches for a nearest point at a body surface position with respect tothe region of interest, and calculates the distance from the region ofinterest to the nearest point as the distance between the body surfaceand the region of interest.

If method 6 (calculation based on the mammary gland density of anobject) is selected in step S6003, the CPU 1001 derives the mammarygland density of the object, and selects the values of α and σcorresponding to the derived mammary gland density as statisticinformation to be used subsequently. In this case, the CPU 1001 derivesthe mammary gland density of the object by the following processing. Forexample, the CPU 1001 calculates a mammary gland density by acquiring abreast region from three-dimensional image data, classifying a fatregion and a mammary gland region in the breast region, and obtainingthe proportion of the mammary gland region included in the breastregion. The breast region is the region from the body surface to thechest wall, and can be acquired by image processing as a region like arange including the mammary gland outer edges of the left and rightbreasts in the body side direction. As the above method of classifyingthe fat region and the mammary gland region in the breast region, forexample, there is available a method of classifying them by performingbinarization processing for the inside of the breast region with a giventhreshold. It is possible to obtain the proportion of the mammary glandregion in the breast region in this manner and use the resultant valueas a mammary gland density. Alternatively, the average value ofluminance values in the breast region may be acquired as a valuerepresenting a mammary gland density. In addition, a local mammary glanddensity near a portion between the nipple and the region of interest maybe obtained in consideration of the position of a region of interest andthe position of the nipple (reference point position). For example, acircular cylinder centered on a line segment connecting the region ofinterest to the nipple and having a predetermined radius may be defined,and a mammary gland density in the range of the circular cylinder may beobtained. Alternatively, the breast region may be divided into blockseach including approximately several tens of voxels, and a mammary glanddensity may be obtained in each block. The weighted average of themammary gland densities in the respective blocks which are weighted inaccordance with the distances from the line segment connecting theregion of interest to the nipple to the respective blocks may be used asa mammary gland density.

Note that when statistic information is held in the form of a functionof input parameters x such as the age of each subject, the breast size,the distance between the nipple and the region of interest, the distancebetween the body surface and the region of interest, the mammary glanddensity, and the like, the magnification α and the standard deviation σare calculate by inputting the parameters associated with the subject tothe function.

(Step S6030: Image Combining)

In step S6030, the CPU 1001 functions as the image generation unit 540to generate an image by superimposing information indicating a placewhere the possibility of the presence of a corresponding region is highon the ultrasonic tomogram based on the ultrasonic tomogram, theposition and orientation of the ultrasonic probe, the reference pointposition, and the corresponding distance. The CPU 1001 then sends thegenerated image to the display unit 180.

First of all, the image generation unit 540 (CPU 1001) obtains spherescentered on the position of the reference point obtained in step S6020and respectively having the corresponding distances (r′−2σ, r′−σ, r′,r′+σ, and r′+2σ) obtained in step S6025 as radii. In this case, fivespheres having the same central position and different radii areobtained.

The image generation unit 540 then obtains a plane in a space containingthe ultrasonic tomogram (that is, an ultrasonic slice (imaging slice))based on the position and orientation of the ultrasonic probe obtainedin step S6010, and calculates circles (five circles) obtained by cuttingthe spheres (five spheres) along the plane. Finally, the imagegeneration unit 540 generates a composite image by superimposingportions (arcs), of the calculated circles, which are included in theultrasonic tomogram, on the ultrasonic tomogram.

FIG. 9 shows an example of the composite image generated by thisprocessing. Referring to FIG. 9, slices of concentric spheres centeredon a nipple position 410 and respectively having corresponding distancesas radii are superimposed as an arc 930 and auxiliary lines 935 on anultrasonic tomogram 440. In addition, pieces of character information(“−2σ”, “−σ”, “σ”, and “2σ”) indicating standard deviations aresuperimposed/displayed as additional information near the respectiveauxiliary lines. Consider the situation shown in FIG. 12A describedabove. Even if the distances between the nipples and the regions ofinterest are the same radius r, information based on statisticinformation in region C is superimposed/displayed in the case of subject1, whereas information based on statistic information in region B issuperimposed/displayed in the case of subject 2, as shown in FIG. 12B.

FIG. 10 is another example of the composite image in this embodiment, inwhich regions falling within the standard deviation σ and regionsfalling within the standard deviation 2σ are translucently colored to bepresented as a presence range 1035. The operator can narrow down thesearch range by searching for a corresponding region 450 while referringto the support information presented in this manner.

With the above operation, it is possible to draw, in an ultrasonictomogram, a position at which the possibility of the presence of acorresponding region is high by using statistic information associatedwith the distance between the nipple and the region of interest, andpresent the resultant image to the operator. In addition, it is possibleto present a position at which the possibility of the presence of acorresponding region is higher by using statistic informationcorresponding to the attributes of an object or a region of interest.Presenting such a position can present a more effective search range tothe operator. This can prevent the operator from making wrongassociation and further reduce the trouble of searching a wide range.

Third Embodiment

The third embodiment is an embodiment configured to make a presentationin consideration of the spatial spread (size) of a region of interest.An information system according to this embodiment will be describedwith reference to only differences from the first embodiment. That is,this embodiment is the same as the first embodiment unless specificallymentioned in the following description.

The information processing system according to this embodiment will bedescribed with reference to the block diagram of FIG. 13. Note that thesame reference numerals as in FIG. 13 denote the same functional unitsas in FIG. 1, and a description of them will be omitted. As shown inFIG. 13, the information processing system according to the embodimentincludes a data server 1360, an information processing apparatus 1300, amedical image collection apparatus 170, and a display unit 180.

The data server 1360 holds information concerning the spatial spread ofa region of interest in addition to information such as the distancebetween the reference point and the region of interest described in thefirst embodiment. In this case, information concerning the spatialspread of a region of interest is, for example, a maximum diameter R ofthe region of interest. Alternatively, the information is the distance(minimum distance Dmin) from a reference point to the nearest point ofthe region of interest and the distance (maximum distance Dmax) to thefarthest point. The former information can be obtained by detecting byimage processing a region indicating a region of interest from thethree-dimensional image data of an object, based on which the distancebetween the reference point and the region of interest is acquired. Thelater information can be calculated based on the nipple position in thethree-dimensional image data and information labeled to a voxel of theregion of interest. The data server 1360 outputs the above held data tothe information processing apparatus 1300.

A display range calculation unit 1310 acquires information concerningthe spatial spread of a region of interest from the data server 1360.The display range calculation unit 1310 then calculates a display rangefor a reference distance based on this information. The display rangecalculation unit 1310 outputs the calculated display range to an imagegeneration unit 1340.

Like the image generation unit 140 in the first embodiment, based on areference distance, the position of a reference point, and the positionand orientation of an ultrasonic probe, the image generation unit 1340superimposes, on an ultrasonic tomogram, the information of an arc whosedistance from the reference point coincides with the reference distance.In addition, the information of a region with a margin with respect tothe reference distance is superimposed on the ultrasonic tomogram byfurther using the value of the display range calculated by the displayrange calculation unit 1310.

Note that when the respective functional units in the informationprocessing apparatus 1300 shown in FIG. 13 are implemented by computerprograms, the computer shown in FIG. 2 can be applied to the informationprocessing apparatus 1300 as in the first embodiment. That is, when therespective functional units in the information processing apparatus 1300are implemented by computer programs, a CPU 1001 executes the computerprograms to make the computer function as the information processingapparatus 1300.

The processing performed by the computer in FIG. 2 which operates as theinformation processing apparatus 1300 will be described next withreference to FIG. 14 showing a flowchart for the processing. Note thatan external storage apparatus 1007 stores computer programs and datawhich make the CPU 1001 execute the processing based on the flowchart ofFIG. 14. The CPU 1001 loads the computer programs and data from theexternal storage apparatus 1007 into a RAM 1002, and executes processingby using the computer programs and data. This makes the computer in FIG.2 execute the processing based on the flowchart of FIG. 14.

Steps S14000, S14010, S14020, and S14040 in FIG. 14 are the same assteps S3000, S3010, S3020, and S3040 in the flowchart of FIG. 3, andhence a description of these steps will be omitted.

(Step S14005: Acquisition of Spatial Spread of Region of Interest)

In step S14005, the CPU 1001 functions as the display range calculationunit 1310 to acquire information concerning the spatial spread of aregion of interest from the data server 1360. For example, the CPU 1001acquires the maximum diameter R of the region of interest and theminimum distance Dmin and the maximum distance Dmax from the referencepoint to the region of interest.

(Step S14007: Calculation of Display Range)

In step S14007, the CPU 1001 functions as the display range calculationunit 1310 to calculate a display range based on the informationconcerning the spatial spread of the region of interest acquired in stepS14005. More specifically, the CPU 1001 determines the lower limit valueand the upper limit value of the distances from the reference pointposition as a display range. If, for example, the maximum radius R ofthe region of interest has been acquired, the range from a lower limitvalue r−R/2 to an upper limit value r+R/2 is set as a display rangebased on a reference distance r. Alternatively, if the minimum distanceDmin and the maximum distance Dmax between the nipple and the region ofinterest have been acquired, the range from the minimum distance Dmin tothe maximum distance Dmax is set as a display range.

(Step S14030: Image Combining)

In step S14030, the CPU 1001 functions as the image generation unit 1340to generate an image by superimposing information indicating a placewhere the possibility of the presence of a corresponding region is highon the ultrasonic tomogram in consideration of the spatial spread of thecorresponding region. More specifically, the CPU 1001 generates acomposite image by superimposing, on the ultrasonic tomogram, thedisplay range acquired in step S14007, that is, arcs respectivelycorresponding to the upper limit value and the lower limit value ofdistances. Alternatively, the CPU 1001 generates a composite image bysuperimposing a region enclosed by the arcs on the ultrasonic tomogramupon translucently coloring the region. Note that the processing ofobtaining an arc on an ultrasonic tomogram which is located at apredetermined distance from a reference point is the same as theprocessing for the reference distance in step S3030 in the firstembodiment, and hence a description of the processing will be omitted.

FIG. 15 shows an example of a composite image in this embodiment. Inthis case, an arc 430 at a reference distance is drawn, and at the sametime, the range enclosed by spheres centered on the reference point andrespectively having radii r−R/2 and r+R/2 is translucently colored andpresented as a presence range 1510.

With the above processing, a presentation is made in consideration ofthe spatial spread of a region of interest. This presentation allows theoperator to perform a search in consideration of the spatial spread ofthe region of interest.

Fourth Embodiment

The pieces of information described as those to be simultaneouslydisplayed on a screen in the above description are not necessarilydisplayed at once. Some of these pieces of information may be displayed,or they may be switched and displayed in accordance with userinstructions.

In addition, according to the above description, a position where thepossibility of the presence of a corresponding region is high is drawnin an ultrasonic tomogram in various forms to be presented to theoperator. However, such a presentation may lead to misunderstandingdepending on the type of lesion, for example, a lesion other than thatdeveloped on a mammary gland. For this reason, this embodiment may beconfigured to switch between performing and not performing the abovecombining processing depending on the type of lesion.

If, for example, the operator identifies the type of lesion anddetermines that the lesion is not the one that develops on a mammarygland, he/she may designate not to perform the above combiningprocessing by using a keyboard 1004 or a mouse 1005.

In addition, there is available so-called “Fusion display” to display anultrasonic tomogram and a corresponding tomogram in thethree-dimensional image obtained by MRI on the same screen side by side.In such Fusion display, although images at the same slice position aredesired to be displayed side by side, the slice positions of therespective images shift during capturing of ultrasonic tomograms due tothe influences of the body motion of a patient and the like.

For this reason, an “alignment mode” and an “imaging mode” are provided.For example, a button image for issuing an instruction to select the“alignment mode” and a button image for issuing an instruction to selectthe “imaging mode” are displayed on a screen of a display unit 180. Whenthe operator designates the button image of the “alignment mode” byoperating the keyboard 1004 or the mouse 1005, a CPU 1001 sets the modeof the computer to the “alignment mode”. On the other hand, when theoperator designates the button image of the “imaging mode” by operatingthe keyboard 1004 or the mouse 1005, a CPU 1001 sets the mode of thecomputer to the “imaging mode”. Note that the mode setting method to beused is not limited to this. When the “alignment mode” is set, the CPU1001 permits the above combining processing. When the “imaging mode” isset, the CPU 1001 inhibits the above combining processing. This makes itpossible to present reference information when the operator adjusts theposition of the ultrasonic prove so as to display images at the sameslice position side by side.

In addition, when performing Fusion display of images in a prone postureand a supine posture, the CPU 1001 may permit the above combiningprocessing, whereas when performing Fusion display of images in supinepostures, the CPU 1001 may inhibit the above combining processing.

As described above, it is possible to permit or inhibit the abovecombining processing in accordance with the purpose or situation of theuse of the information processing system. In addition, the CPU 1001 maypermit/inhibit combining processing of only arcs and pieces of characterinformation corresponding to the arcs (for example, 5 mm, 10 mm, 15 mm,and the like) instead of inhibiting or permitting the entire combiningprocessing. It is also possible to perform control to display a specificnumber of sets of arcs and pieces of character information correspondingto the arcs instead of permitting/inhibiting combining processing. Forexample, the number of display sets is increased in the above “alignmentmode”, whereas the number of display sets is decreased in the “imagingmode”. Alternatively, the operations described above may be combined asneeded.

As has been described above, the essence of the above description isbased on the technique of acquiring a tomogram of an object, specifyinga place in the tomogram which corresponds to a portion spaced apart froma reference point in the object by a predetermined distance, andgenerating and outputting a composite image having informationindicating the specified place on the tomogram.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (e.g., non-transitorycomputer-readable storage medium) to perform the functions of one ormore of the above-described embodiment(s) of the present invention, andby a method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiment(s). The computer may comprise one or more ofa central processing unit (CPU), micro processing unit (MPU), or othercircuitry, and may include a network of separate computers or separatecomputer processors. The computer executable instructions may beprovided to the computer, for example, from a network or the storagemedium. The storage medium may include, for example, one or more of ahard disk, a random-access memory (RAM), a read only memory (ROM), astorage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2013-188717, filed Sep. 11, 2013, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An information processing apparatus comprising: aunit configured to acquire a tomogram of an object; and a generationunit configured to specify a place in the tomogram which corresponds toa portion spaced apart from a reference point in the object by apredetermined distance, generate a composite image by combining thetomogram with information indicating the specified place, and output thecomposite image.
 2. The apparatus according to claim 1, wherein saidgeneration unit obtains a circle by cutting a sphere centered on aposition of the reference point and having the predetermined distance asa radius along an imaging slice of the object which corresponds to thetomogram, and obtains an arc, of the obtained circle, which is includedin the tomogram as the place.
 3. The apparatus according to claim 2,wherein said generation unit generates a composite image bysuperimposing the arc on the tomogram and outputs the composite image.4. The apparatus according to claim 2, wherein said generation unitgenerates a composite image by superimposing a character indicating thepredetermined distance on the tomogram and outputs the composite image.5. The apparatus according to claim 1, wherein the predetermineddistance comprises a reference distance and a plurality of distancesdifferent from the reference distance, and said generation unitspecifies places in the tomogram which correspond to portions spacedapart from the reference point by the respective distances included inthe predetermined distance, generates a composite image by combining thetomogram with pieces of information indicating the places specified inthe tomogram with respect to the respective distances, and outputs thecomposite image.
 6. The apparatus according to claim 1, wherein thepredetermined distance comprises a plurality of distance set at equalintervals, and said generation unit specifies places in the tomogramwhich correspond to portions spaced apart from the reference point bythe respective distances included in the predetermined distance,generates a composite image by combining the tomogram with pieces ofinformation indicating the places specified in the tomogram with respectto the respective distances, and outputs the composite image.
 7. Theapparatus according to claim 1, further comprising a unit configured toset, as a reference distance, a distance serving as a reference for thepredetermined distance, and obtain, as the predetermined distance, anestimated value of the reference distance when the reference distancechanges with a change in body posture.
 8. The apparatus according toclaim 1, wherein, in accordance with a mode designated by a user, saidgeneration unit outputs the tomogram without generating the compositeimage or generates and outputs the composite image.
 9. The apparatusaccording to claim 1, wherein the object comprises a breast, thereference point comprises a nipple of the breast, and the predetermineddistance comprises a three-dimensional distance from the nipple to alesion.
 10. An information processing apparatus comprising: a unitconfigured to acquire a tomogram of an object; a unit configured toacquire a predetermined distance as a distance from a reference point inthe object to a lesion in the object; a unit configured to specify aplace in the tomogram which corresponds to a portion spaced apart from aposition of the reference point by the predetermined distance; and aunit configured to combine information indicating the place with thetomogram and output a composite result.
 11. An information processingmethod performed by an information processing apparatus, comprising: astep of acquiring a tomogram of an object; and a generation step ofspecifying a place in the tomogram which corresponds to a portion spacedapart from a reference point in the object by a predetermined distance,generating a composite image by combining the tomogram with informationindicating the specified place, and outputting the composite image. 12.An information processing method performed by an information processingapparatus, comprising: a step of acquiring a tomogram of an object; astep of acquiring a predetermined distance as a distance from areference point in the object to a lesion in the object; a step ofspecifying a place in the tomogram which corresponds to a portion spacedapart from a position of the reference point by the predetermineddistance; and a step of combining information indicating the place withthe tomogram and outputting a composite result.
 13. A non-transitorycomputer-readable storage medium storing a computer program for causinga computer to function as each unit of an information processingapparatus defined in claim
 1. 14. An information processing apparatuscomprising: a tomogram acquisition unit configured to acquire a tomogramof an object; a reference point position acquisition unit configured toacquire a three-dimensional position of a reference point in the object;a position and orientation acquisition unit configured to acquire aposition and orientation of the tomogram; and a display unit configuredto superimpose and display, on the tomogram, information concerning athree-dimensional distance from the reference point to each point on thetomogram based on the three-dimensional position of the reference pointand the position and orientation of the tomogram.
 15. The apparatusaccording to claim 14, further comprising a reference distanceacquisition unit configured to acquire a reference distance as athree-dimensional distance from the reference point to a region ofinterest, wherein information displayed by said display unit comprisesinformation indicating a relationship between the reference distance anda three-dimensional distance from the reference point to each point onthe tomogram.
 16. The apparatus according to claim 15, whereininformation displayed by said display unit comprises informationindicating a point, on the tomogram, whose three-dimensional distancefrom the reference point coincides with the reference distance.
 17. Theapparatus according to claim 14, further comprising: a referencedistance acquisition unit configured to acquire a reference distance asa three-dimensional distance from the reference point to a region ofinterest; and a corresponding distance calculation unit configured tocalculate a corresponding distance based on the reference distance,wherein information displayed by said display unit comprises informationindicating a relationship between the corresponding distance and athree-dimensional distance from the reference point to each point on thetomogram.
 18. The apparatus according to claim 17, wherein saidcorresponding distance calculation unit calculates the correspondingdistance based on a mammary gland density of the object.